To USB or Not to USB

USB only Monitor from Samsung

Samsung demonstrated a USB only monitor at the Society for Information Display conference last week in Oregon. The screen uses a forked USB 2.0 connector to provide the power necessary. This is only possible because this is an edge-lit LED display.

Also, at Everything USB, the author speculates that with USB 3.0 you could maybe use a single USB 3.0 port. I’ve run the math below and my commentary is at the end of this blog entry.

Current

Voltage

Power per port

Comment

USB 2.0

500mA

5V

2.5W

USB 3.0

900mA

5V

4.5W

USB 3.0 with modified power like on Gigabyte motherboard

2700mA

5V

13.5 W

One modified USB 3.0 port will work like those find on Gigabyte motherboards

I should point out that some USB 2.0 devices pull more than the legal 500mA from a Host, and when they do, they violate the specification.

The interesting thing that TechOn reports that the display requires 6.3 W. You can see from the calculations above, that 2 USB 2.0 ports will only generate about 5 W. This means that either the actual average power requirement is much lower than 5W, or there is some power savings scheme on the screen when running on USB. My hope is that displays would run at even lower power and could run off off a single USB 3.0 port.

Eric started working on USB in 1995, starting with the world’s first BIOS that supported USB Keyboards and Mice while at Award Software. After a departure into embedded systems software for real-time operating systems, he returned to USB IP cores and software at inSilicon, one of the leading suppliers of USB IP. In 2002, inSilicon was acquired by Synopsys and he’s been here since. He also served as Chairman of the USB On-The-Go Working Group for the USB Implementers Forum from 2004-2006.

Eric received an M.B.A. from Santa Clara University and an M.S. in Engineering from University of California Irvine, and a B.S. in Engineering from the University of Minnesota. and is a licensed Professional Engineer in Civil Engineering in the State of California.